1. Field of the Invention
The present invention relates to a semiconductor ceramic and positive-temperature-coefficient thermistor, and particularly relates to a semiconductor ceramic and positive-temperature-coefficient thermistor having high resistance temperature properties, with high-flash-breakdown capability necessary with degaussing for color televisions, motor starters, overcurrent protectors and so forth.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 6-215905 discloses a semiconductor ceramic wherein erbium is contained as a semiconducting agent in primary components of barium titanate, lead titanate, strontium titanate and calcium titanate, which are used for degaussing in color televisions.
Also, Japanese Unexamined Patent Application Publication No. 2000-143338 discloses a semiconductor ceramic wherein samarium oxide is contained as a semiconducting agent in primary components barium titanate, lead titanate, strontium titanate and calcium titanate, with the average grain diameter of the semiconductor ceramic being between 7 to 12 xcexcm.
However, each of the above semiconductor ceramics have inferior high-flash-breakdown capability, exhibit unsatisfactory results in ON-OFF application tests, and also had great irregularities in specific resistance values at room temperature. Accordingly, a semiconductor ceramic and positive-temperature-coefficient thermistor having high resistance temperature properties with high-flash-breakdown capability such as necessary for degaussing for color televisions, motor starters, overcurrent protectors and so forth, has not been obtained.
Accordingly, it is an object of the present invention to provide a semiconductor ceramic and positive-temperature-coefficient thermistor which has high-flash-breakdown capability, exhibits excellent results in ON-OFF application tests and also has few irregularities in specific resistance values at room temperature.
To this end, the semiconductor ceramic according to the present invention is a semiconductor ceramic wherein erbium is contained as a semiconducting agent in primary components barium titanate, strontium titanate, lead titanate and calcium titanate, with the average grain diameter of the semiconductor ceramic exceeding about 5 xcexcm but not exceeding about 14 xcexcm.
The semiconductor ceramic with the above composition has high-flash-breakdown capability, exhibits excellent results in ON-OFF application tests and has few irregularities in resistance values.
The semiconductor ceramic according to the present invention preferably contains an additive compound containing Er with the Er being more than about 0.10 mol but no more than about 0.33 mol, a compound containing Mn with the Mn being about 0.01 mol or more but no more than about 0.03 mol, and a compound containing Si with the Si being about 1.0 mol or more but no more than about 5.0 mol, per 100 mol of the primary component.
Further, the positive-temperature-coefficient thermistor according to the present invention comprises an element member of the semiconductor ceramic with electrodes provided on the front and back sides.